Never heard of this. And Sonos wouldn’t be sending a new volume signal when you hit resume, I’d think, it should be resuming at whatever level it was when paused. But that’s a guess. You could probably recreate the issue, then submit a system diagnostic, and call Sonos Support to discuss it. They should, I’d expect, to see where the volume change command is coming from.
I’m having the same issue with an LG TV
What did Sonos Support say?
Haven’t contacted them yet… I just started noticing the behavior when I upgraded my Beam to an Arc.